Field of the Invention
This invention relates to mobile communication devices and more particularly to an improved antenna and filter architecture for RF front end circuits to enhance communication system performance.
Description of the Related Art
As multimode systems become more common and as more frequency bands are added to communication systems filtering requirements become more complex and difficult. As more filtering is added the losses in the system increase, which in turn reduces communication range and data rate of transmitted signals, or required additional transmit power to overcome these increased losses.
A common problem encountered in mobile wireless communication systems is the de-tuning effects incurred on the antenna due to the multiple use cases for the device. As the antenna de-tunes, the impedance presented by the antenna to the power amplifier and receiver varies, which in turn reduces the power transfer through the front end (power amplifier, switch assembly, filters, and antenna). The result is reduced communication range as well as reduced data rate for the communication device. With a passive antenna and fixed impedance matching circuit, the front end can only be optimized for a single use case such as device held in the user's hand, device against the user's head, or placement of the device on a surface such as a table or dashboard of an automobile. The added requirement for the mobile wireless device to operate when connected to or in close proximity to additional accessories makes the task of keeping the antenna system optimized more of a challenge.